This is a 30-year-old woman referred to our unit at 32 weeks due to a left pyelectasis. The nuchal translucency and triple test were normal. At 24 weeks, the scan was normal. The third scan was performed at 32 weeks. The growth was normal as well as the amniotic fluid. There was a left pyelectasis with left ureteral dilatation. The bladder was normal. The right and left corticomedullary differentiation were normal. These anomalies were confirmed at 34 weeks.

At day 3 of life, the pyelectasis was still present (12 mm) with ureteral dilatation. The cystography did not reveal any reflux. One month later, the pyelectasy was still present (6 mm). But the ureteral dilatation was severe (7 to 10 mm). Nevertheless the kidney corticomedullary differentiation was normal. The left megaureter diagnosis was confirmed. The baby received penicillin during the first six months of life.